The Collaborative International Dictionary of English v.0.48:

Whitethroat \White"throat`\, n. (Zool.)
   Any one of several species of Old World warblers, esp. the
   common European species (Sylvia cinerea), called also
   strawsmear, nettlebird, muff, and whitecap, the
   garden whitethroat, or golden warbler (Sylvia
   hortensis), and the lesser whitethroat (Sylvia curruca).
   [1913 Webster]

WordNet (r) 3.0 (2006):

lesser whitethroat
    n 1: Old World warbler similar to the greater whitethroat but
         smaller [syn: lesser whitethroat, whitethroat, Sylvia
         curruca]